RESUMO
A silver nanoparticles (AgNPs)-integrated terahertz (THz) metasurface sensor was presented and applied to enhance the sensitivity of substance detection. Simulations and experiments were conducted to study the influence of AgNPs on the sensor performance. The enhancement of the local electric field excited by AgNPs can substantially strengthen the interaction between the THz waves and analytes, thereby increasing detection sensitivity. The experimental results indicate that the detection limit of the AgNPs-integrated metasurface sensor is improved by two orders of magnitude compared to that of the bare metasurface sensor without AgNPs. This study provides a convenient method to enhance the sensitivity of THz metasurface sensors.
RESUMO
Spatial frequency-based information plays an important role in visual perception. By combining behavioral and electroencephalogram (EEG) measurements, we investigated the mechanisms of the interaction and information integration between different spatial frequency bands. The observers performed a scene categorization task on hybrid images that were generated by combining the low spatial frequency (LSF) component of one image with the high spatial frequency (HSF) component of another image. The results showed that the recognition of the HSF component was interfered by the non-attended LSF component at semantic level. The strength of the semantic interference was modulated by the physical similarity between the LSF and HSF components. Analyses of the EEG data revealed an early anterior N1 component (122 ms from stimulus onset) that was related to the observed interaction of the semantic and physical information between the LSF and HSF components. These findings demonstrate that the semantic information from different spatial frequency bands can be integrated at early stage of the perceptual processing. This early integration is likely to occur at frontal areas in order to initiate top-down facilitation.